P0506 & P0507 Codes: Idle Speed Lower or Higher Than Expected (GM Guide)

P0506 means the engine is idling lower than the module asked for. P0507 means it is idling higher. They are opposite ends of the same diagnostic, and the direction tells you where to look. Most of the time the answer is carbon in the throttle body and a relearn that costs nothing. But there are two things worth knowing before you reach for the cleaner: on turbocharged GM crossovers, a charge air cooler pipe blows off the throttle body, and on GM V8s, P0506 together with a misfire code has been linked to a broken valve spring.

What Do P0506 and P0507 Mean?

At idle, the engine needs a small, precisely controlled amount of air. On modern GM vehicles there is no separate idle air valve — the electronic throttle body holds the plate slightly open and the module adjusts that opening continuously to hold the target speed.

The module knows what idle speed it wants, and it can see what it is getting.

Code	What it means	What that implies
P0506	Actual idle is lower than desired	The engine is not getting enough air, or something is loading it down. Carbon restriction is the classic cause
P0507	Actual idle is higher than desired	The engine is getting more air than commanded. Unmetered air — a vacuum leak — is the classic cause

That direction is genuinely useful. P0506 sends you looking for a restriction; P0507 sends you looking for a leak. They are close to opposite searches, and treating them as one generic "idle problem" wastes the clue the code just handed you.

GM's Set Condition

Knowing the threshold explains why these codes behave as they do.

On GM trucks, P0506 sets when actual engine speed is roughly 90 RPM below the desired idle speed for more than 10 seconds. Reported run conditions require the engine to be warm — coolant temperature above about 60°C (140°F) — and intake air temperature above roughly −20°C (−4°F), with the throttle closed.

Three things follow:

• The monitor does not run cold. A rough cold idle that clears as the engine warms will not set this code, because the diagnostic has not started yet.
• It needs a sustained deviation. A momentary dip does not qualify — 10 seconds of being 90 RPM low does.
• Freeze frame is worth reading. Reported cases show actual RPM in the 300–400 range against a desired 700–800, which is a very large gap and points at something substantial rather than marginal.

For reference, healthy idle control keeps actual speed within roughly 50 RPM of desired, typically somewhere in the 600–800 RPM range depending on the engine.

The Charge Air Cooler Pipe — Turbo Crossovers

This is the check that takes thirty seconds and can save a diagnostic bill.

On 2018–2022 Equinox and its platform relatives — Terrain and Malibu — with turbocharged engines, GM has issued multiple bulletins about the charge air cooler outlet pipe disconnecting from the throttle body.

When that pipe blows off, everything the turbocharger is pushing escapes before it reaches the engine. The result is a massive unmetered air leak, and the symptoms are dramatic:

• Low, unstable idle and stalling
• Reduced engine power — reported as being unable to accelerate past about 45 mph
• A very obvious loss of performance rather than a subtle one

GM's answer includes an updated retainer clip, which tells you the original retention was the weak point rather than the pipe itself.

So: if you have a turbocharged GM crossover with P0506 and reduced power, open the hood and look at where the charge air cooler pipe meets the throttle body before anything else. A pipe that has popped off is visible immediately, and reconnecting it with the updated clip is the whole repair.

This one is worth checking even if the pipe looks attached — a partially seated pipe leaks without falling off entirely.

P0506 With a Misfire — the Branch That Matters

This is the most important warning on the page, and it runs against the obvious diagnosis.

P0506 usually means carbon. But on 2014–2021 Silverado and Sierra, the combination of P0506 with a misfire code such as P0300 — and sometimes P0106 — has been linked in GM bulletins to a broken valve spring.

The mechanism makes sense once stated. A broken valve spring means a valve that does not close properly. That cylinder cannot hold its share of the load at idle, the engine drops below its target speed, and it misfires. Both codes come from one mechanical failure.

Why this matters so much: the intuitive response to P0506 is to clean the throttle body. On a truck with a broken valve spring, that achieves nothing — and it delays finding a mechanical fault that can progress. A valve that is not closing correctly is not a stable condition.

The rule: if P0506 arrives with any misfire code on a GM V8, do not assume carbon. Ask for the mechanical side to be assessed. A cylinder-specific misfire alongside makes the case stronger still.

Our P0300 guide covers the misfire side, and our P219A guide covers another code where a single cylinder failing mechanically produces a symptom that looks like something else entirely.

Carbon — and Why the PCV System Causes It

With those two exceptions covered, the common cause is exactly what you would expect.

Carbon and oil residue build up in the throttle bore and around the plate. Because the plate only opens a tiny amount at idle, a deposit thick enough to matter at idle is far too thin to notice at any other throttle position — which is why the engine drives normally and only misbehaves at a stop.

The reason it accumulates is worth understanding: the positive crankcase ventilation system routes crankcase vapours — which carry oil mist — into the intake. On some engines, notably the 2.4L Ecotec, that design puts a steady supply of oil vapour past the throttle plate, where it bakes onto the bore and collects carbon.

Two practical consequences:

• It comes back. Cleaning fixes the symptom; the PCV system keeps supplying the cause. On affected engines, treat throttle body cleaning as periodic maintenance rather than a permanent repair.
• It is cheap. Reported at well under twenty dollars in cleaner and about an hour of work — which makes it worth doing before anything is replaced.

How to inspect: remove the intake duct and look at the throttle bore. You are looking for a ring of black deposit around the plate where it seats. Spray cleaner onto a cloth rather than into the manifold, and clean the bore and both faces of the plate.

The Relearn You Must Not Skip

This is where a successful cleaning turns into a returning code.

The module learns where the closed-throttle position is and how much opening produces a given idle speed. When you clean the throttle body, you have just changed that relationship — the same plate position now flows considerably more air.

Without a relearn, the module is applying compensation it worked out for a dirty throttle body to a clean one. The result is a high or unstable idle, or the same code coming straight back.

An idle relearn is required after:

• Cleaning or replacing the throttle body
• Disconnecting the battery for an extended period
• Any repair that changes airflow at idle

The manual procedure reported for GM applications is straightforward: let the engine idle for three minutes, switch it off for sixty seconds, then idle for three minutes again. No scan tool required.

A capable scan tool can perform a guided idle learn or throttle relearn instead, and on some applications that is the proper route. Our P1516 guide covers the same relearn requirement from the other direction — GM documents that skipping it brings the concern back with P0121, P0506 and P0507 alongside, which is exactly the situation this section exists to prevent.

What P0507 Points At Instead

Because the direction is reversed, so is the search.

P0507 means more air is reaching the engine than the module commanded — so the question is where that extra air is entering without being measured.

• Vacuum leaks — the classic cause. Cracked hoses, a failed intake gasket, a leaking brake booster hose, a loose PCV connection.
• The charge air cooler pipe on turbo applications, which can produce either code depending on the engine's response.
• A throttle plate not closing fully, whether from carbon holding it open or a mechanical problem.
• A relearn that was never done after cleaning — the classic self-inflicted high idle.
• A sticking or failed idle air control valve on older designs that still use one.

The best tool for P0507 is a smoke test, which finds unmetered air far more reliably than listening or spraying. If you have P0507 with lean fuel trim codes such as P0171 alongside, that combination points hard at a vacuum leak — see our P0171 guide.

One more useful companion: P0505 stored alongside suggests an electrical problem in the idle control system — wiring or the control component itself — rather than a mechanical restriction or leak.

A Note on Sourcing for These Codes

We cite documents we have read and label the rest.

The GM bulletins referenced here are corroborated from technician-facing sources rather than opened by us — including the charge air cooler pipe documents for the turbo crossovers, the valve spring link on 2014–2021 trucks, and preliminary information reported as PIP5710A and PIP5651G for the 2010–2017 Equinox 2.4L.

The 90 RPM and 10 second set condition, the temperature run conditions, and the three-minute manual relearn procedure are reported rather than confirmed by us against GM's documentation.

The valve spring link is the one to verify for your specific vehicle, because it is the difference between a twenty-dollar cleaning and a mechanical repair. Ask a dealer to check your VIN against current bulletins — free, and on this particular combination of codes it genuinely matters.

Symptoms of P0506 and P0507

• Check engine light on
• Stalling when coming to a stop — the most reported symptom with P0506
• Rough, low or hunting idle
• Idle that stays high and does not settle, with P0507
• Idle dropping when the air conditioning or another load engages
• Hesitation pulling away from a stop
• Reduced engine power, particularly where a charge air cooler pipe has disconnected
• Poor fuel economy

On urgency: moderate, and the stalling is why. An engine that quits as you come to a stop is a hazard in traffic — you lose power steering assist and brake assist at the moment you most need them. That is a different matter from a light on the dash. If yours is stalling, deal with it promptly. If it is a mildly rough idle with no stalling, you have more time.

Causes and How to Confirm Each

Cause	How to confirm it	Which code
Charge air cooler pipe off the throttle body	Visually inspect where the pipe meets the throttle body. Check it is fully seated, not just attached	Turbo crossovers. Look here first
Broken valve spring	P0300 or a cylinder misfire alongside. Mechanical assessment	P0506 on 2014–2021 V8 trucks. Do not just clean
Carbon in the throttle bore	Remove the intake duct; look for a black ring around the plate	Mainly P0506. The common cause
Idle relearn not performed	Did the code follow a throttle body cleaning, replacement, or a long battery disconnect?	Either — often P0507
Vacuum leak	Smoke test the intake. Check hoses, gaskets, the brake booster line and PCV connections	Mainly P0507
Restricted air filter or collapsed intake duct	Inspect the filter and duct — a basic first check	P0506
Throttle body failure after cleaning	Where a thorough clean and relearn did not resolve it and no leaks are found	Either
Throttle position sensor fault	TP sensor voltage should sweep smoothly — roughly 0.5 V closed to 4.5 V open, with no dropouts	Either. See our P2135 guide
Electrical fault in the idle control system	P0505 stored alongside — wiring rather than carbon	Either
PCV system fault	Inspect the PCV components; a stuck-open valve is an unmetered air path	Mainly P0507

How Are P0506 and P0507 Diagnosed?

1. Note which code you have. Low means restriction; high means unmetered air. Those are different searches.
2. Record every stored code. A misfire alongside P0506 on a V8 changes the diagnosis entirely; P0505 points at wiring; lean codes point at a leak.
3. On a turbo crossover, inspect the charge air cooler pipe at the throttle body. Thirty seconds, and a documented cause.
4. Ask what work was done recently. A throttle body cleaning or a long battery disconnect without a relearn explains a great many of these.
5. Check the air filter and intake duct for restriction or collapse.
6. Remove the intake duct and inspect the throttle bore for a carbon ring around the plate.
7. Smoke test the intake, particularly for P0507.
8. Clean the throttle body where carbon is found — cleaner on a cloth, not sprayed into the manifold.
9. Perform the idle relearn. Three minutes idling, sixty seconds off, three minutes idling — or the guided procedure with a capable tool.
10. If a misfire is present, assess the mechanical side rather than repeating the cleaning.
11. Verify over several drive cycles, including full warm-up, since the monitor only runs once the engine is hot.

Parts and Cost

Repair	What it involves	Cost picture
Reconnect the charge air cooler pipe	Reseat the pipe, fit the updated retainer clip	Minimal. Check before any diagnosis is billed
Idle relearn	Three minutes on, sixty seconds off, three minutes on	Free. And it resolves a surprising number of these
Throttle body cleaning	Cleaner, a cloth, an hour, plus a gasket if disturbed	Reported well under twenty dollars in materials
Air filter	Where restriction is found	Minimal
Vacuum hose or gasket	Where a smoke test finds the leak	Modest
PCV components	Where the ventilation system is the leak or the carbon source	Modest
Throttle body assembly	Where cleaning and relearn did not resolve it. Bolt-on, then relearn	Moderate — confirm before ordering
Valve spring repair	Where a misfire alongside points at mechanical failure	Substantially more. But cleaning a throttle body will not fix it

Confirm any part against your VIN. Throttle bodies differ between engines and are not interchangeable across the range.

What Other P0506 / P0507 Pages Get Wrong

• Treating the two codes as one problem. Low idle points at a restriction; high idle points at unmetered air. The direction is a free clue and most write-ups discard it.
• Assuming carbon when a misfire is present. On 2014–2021 GM V8 trucks, P0506 with P0300 has been linked to a broken valve spring. Cleaning the throttle body on that vehicle achieves nothing and delays a real mechanical repair.
• Never mentioning the charge air cooler pipe. On turbo GM crossovers it disconnects from the throttle body, produces reduced power and a low unstable idle, and GM issued an updated retainer clip for it. It is visible in seconds.
• Skipping the relearn. Cleaning a throttle body changes how much air a given plate position flows. Without a relearn the module applies old compensation to a clean throttle body — and the code returns, often as a high idle.
• Not explaining that carbon recurs. The PCV system keeps routing oil vapour into the intake. On affected engines this is maintenance, not a one-time fix.
• Recommending spraying cleaner into the intake. Cleaner belongs on a cloth. Flooding the manifold sends solvent somewhere it should not go.
• Calling stalling a minor symptom. An engine that quits as you come to a stop takes power steering and brake assist with it, in traffic. That deserves prompt attention.
• Ignoring P0505 alongside. It moves the diagnosis from mechanical restriction toward an electrical fault in the idle control circuit.

Frequently Asked Questions

What's the difference between P0506 and P0507?

P0506 means idle speed is lower than the module wanted; P0507 means it is higher. Low points at a restriction — usually carbon in the throttle body. High points at extra air getting in that the module did not command, which usually means a vacuum leak. They are close to opposite searches.

Will cleaning the throttle body fix it?

Often, on P0506 — but only if you also perform the idle relearn afterwards. Cleaning changes how much air a given throttle position flows, and without a relearn the module keeps applying its old compensation, which brings the code back or produces a high idle instead.

How do I do an idle relearn without a scan tool?

The reported manual procedure for GM applications is: let it idle for three minutes, switch off for sixty seconds, then idle for three minutes again. A capable scan tool can run a guided idle learn instead, which is the proper route on some applications.

I have P0506 and a misfire code. Is that just a dirty throttle body?

Probably not, and this is the most important thing on this page. On 2014–2021 Silverado and Sierra, P0506 together with P0300 has been linked in GM bulletins to a broken valve spring. A valve that will not close properly drops idle speed and misfires — one mechanical fault producing both codes. Get the mechanical side assessed rather than cleaning.

My turbo Equinox has low idle and won't go past 45 mph. What is it?

Open the hood and look at where the charge air cooler pipe meets the throttle body. On 2018–2022 Equinox, Terrain and Malibu with turbo engines, that pipe disconnecting is a documented cause, and GM issued an updated retainer clip for it. Everything the turbo pushes is escaping before it reaches the engine.

Why does the carbon keep coming back?

Because the PCV system routes crankcase vapours carrying oil mist into the intake, past the throttle plate. On some engines — the 2.4L Ecotec in particular — that is a design characteristic rather than a fault. Treat throttle body cleaning as periodic maintenance on those engines.

Can I drive with these codes?

If it is a slightly rough idle with no stalling, you have some time. If it stalls when you come to a stop, deal with it promptly — a stall in traffic costs you power steering and brake assist at the worst moment. And if reduced power is involved, that is its own hazard.

Why did the code appear right after I disconnected the battery?

Because the module lost its learned idle values. An extended battery disconnect is one of the situations that requires an idle relearn, exactly like a throttle body cleaning. Run the relearn procedure before assuming anything is broken.

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